c - 如何将数据从结构或联合复制到没有空字符的缓冲区数组？

Question

我正在将 conf 数据从 struct 处理到 char 数组缓冲区。数据已成功复制，但问题是 null 也因大小而从结构中复制。我怎样才能得到没有 null 的数据。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_DEVICE    5
#define MAX_CONF_PORT 3

typedef struct
{
  unsigned char id[6];
  unsigned char domain[32];
  unsigned char ports[MAX_CONF_PORT][5];
}DEV_CONF_DATA; 

#define SIZE_OF_DEV_CONF_DATA sizeof(DEV_CONF_DATA)

typedef union {
  DEV_CONF_DATA data;
  unsigned char bytes[SIZE_OF_DEV_CONF_DATA];   
}DEV_CONF_BUFF;

typedef struct {
    DEV_CONF_BUFF conf[MAX_DEVICE];
}DEVICE;

int main()
{
  int i = 0;
  DEVICE device;
  unsigned char tx_buff[1024];
  unsigned char *dest_ptr = tx_buff;

  device.conf[0].data= (DEV_CONF_DATA) {"ABC,","embed-service.net,","8111,","8112,",","};
  device.conf[1].data= (DEV_CONF_DATA) {"XYZ,","embed-service.net,","7111,","7112,",","};

  memcpy(dest_ptr,device.conf[0].bytes,SIZE_OF_DEV_CONF_DATA);
  dest_ptr += SIZE_OF_DEV_CONF_DATA;
  memcpy(dest_ptr,device.conf[1].bytes,SIZE_OF_DEV_CONF_DATA);
  dest_ptr += SIZE_OF_DEV_CONF_DATA;

   for(i=0;i<SIZE_OF_DEV_CONF_DATA;i++)
       if( tx_buff[i] == 0)
       printf("%s", " null ");
       else
       printf("%c", tx_buff[i]);

   printf("\n\n\n");

   for(i=SIZE_OF_DEV_CONF_DATA;i<SIZE_OF_DEV_CONF_DATA*2;i++)
       if( tx_buff[i] == 0)
       printf("%s", " null ");
       else
       printf("%c", tx_buff[i]);
}

这是我的输出：

ABC, null null embed-service.net, null null null null null null null null null null null null null 8111,8112, null null null null

XYZ, null null embed-service.net, null null null null null null null null null null null null null 7111,7112, null null null null

我想要像这样在缓冲区中整洁干净的数据，

ABC,embed-service.net,8111,8112,,XYZ,embed-service.net,7111,7112,,